Been trying to remember to google this for months, finally rememebred to today but couldn't find an answer...

Why does an incoming tide increase wave height? It's said all the time by everyone 'wait for the push and there'll be an alright wave', yet nobody seems to know quite why... Does seem to be the truth too.

I don't know exactly but it's possibly influenced by the water movement and the water depth.

May be it's more like when the tide is pulling, the water movement is flowing away from the shore, so the waves are tinier, rather than pushing tide making the waves bigger? But 3-4m of water depth over 6hr time, how much of water movement can humans notice or feel? I have a doubt on that.

Or maybe the sets during the push is bigger as the water movement is towards the shore.

See, that's interesting. If a spot works at HT or LT, then may be it doesn't matter if the tide is on the push or pull.

The closest spot to surf for me works somewhere in mid-tide. And everyone here says it's better on the push. Still good when pulling, but the general consensus is that it's "better" on the push. But why and really? This is what you're asking isn't it, Kabazz?

Last edited by defever on Fri Apr 26, 2013 8:48 am, edited 1 time in total.

I turn up, if its looking ok I get in. I would say N. Devon is better on the push because the incoming tide is squeezed into a narrowing estuary so you get a swell build. Exposed places like w/nw corn a sucking outflow tide can be good but just depends on the place & what works there.

I thought defever had the right idea; incoming tide means that there is less backflow to affect the shape and size of the waves. I don't think this is always the case, depends on many factors; beach shape etc. I think it's often the case in the Bristol Channel as it has the second biggest tide variance in the world (I think).

There's a local point I actually prefer to surf on a dropping tide as it gets bigger as the tide drops and I can stay tuned in as it gets bigger.

Basically the incoming tide is essentially a wave - so it therefore increases the average wave height per set - for greater detail read Tony Butt's 'Surf Science'

We get the pushmepullyou waves a lot in Wales ^ Exactly the same as Blacks evidence for north devon. Also depends on tidal range and we have a 10m in S Wales - Jersey has a 14m so you can nearly guarantee a 1ft wave on the push, even when flat (ish)

Water depth certainly has a big part to play especially in areas where the seabed is gently sloping or there are large shallow areas offshore, less so in more exposed coasts.

Wave current interaction is a fascinating part of physical oceanography, its also a total mind fvck when you tr and consider it in practice. currents can refract waves, shift them in frequency space and dissipate wave energy - to the extent waves can be completely blocked if an opposing current approaches the wave group speed.

In south wales its very complicated, the currents are strong enough to approach a blocking scenario on the outgoing tide or a least significantly reduce wave heights, hence why it can be completely flat on the drop and 5ft on the push, then you've got the sandbars which block swell to some places at low tide, and the fact that theres strong longshore currents and curent gradients will refract the waves such that the angle of incidence changes. I can think of a couple of places that have good quality rights with the tide in one direction and good quality lefts with the tide in the other!